Indrawati, 47, quit Wednesday to take the number-two job at the World Bank after months of bruising exchanges with lawmakers intent on ousting her over a controversial bank bailout in 2008.

But in the absence of any clear explanation for the move from either Indrawati or President Susilo Bambang Yudhoyono, her biggest backer, the rumour mill is spinning about her motives and what her departure means.

"Sri Mulyani's departure is a loss to Indonesia," Standard Chartered's senior economist in Indonesia, Fauzi Ichsan, said of the independent policy expert who was named "finance minister of the year" in 2006 by Euromoney magazine.

"Sri Mulyani is a true icon for Indonesian reform. There are many people here who excel in macroeconomics but only a few who possess the ability and courage to reform the bureaucracy."

After tumbling 3.81 percent the day of her resignation the Indonesian share market shed another 2.1 percent by midday Thursday, weighed as much by Europe's debt crisis as Indrawati's announcement, dealers said.

The rupiah had slumped around 3.35 percent against the dollar to 9,250 since Indrawati's resignation became public on Wednesday morning.

Indonesia, a country of 234 million people, now has no full-time central bank governor and no new finance minister as it tries to attract billions of dollars in foreign investment deemed vital to maintaining high growth.

Investment has surged this year amid hopes that the government is at last serious about slashing red tape and getting a grip on rampant corruption that has fouled Indonesia's reputation for decades.

Much of that confidence rested on Indrawati's slight shoulders. Her uncompromising attitude to graft -- she punished almost 2,000 finance ministry personnel and dishonourably discharged at least 150 -- was seen as a model for other ministers to follow.

She also led the charge to enforce the country's tax laws and plug gaping holes that cost the state many billions in unpaid dues -- money badly needed for basic things like roads, ports, schools and hospitals.

Some analysts traced Indrawati's problems to 2008, when she upset the country's most powerful tycoon, Golkar party chief Aburizal Bakrie, by refusing to shield his family's Bumi Resources from a stock market sell-off. Considered one of Asia's most powerful women, she also clashed with Bakrie over unpaid mining royalties and taxes, and accused him of a campaign to discredit her.

Golkar was one of two parties that sought her ouster over the bank bailout, although she has always denied any wrongdoing. A recent survey of 33 senior business managers in the oil and gas business by PriceWaterhouseCoopers found that legal uncertainty and corruption remained two of the biggest obstacles to doing business in Indonesia.

Yudhoyono has repeatedly pledged to tackle corruption since his election in 2004 but respondents said they had seen little change over the past five years. The head of Transparency International Indonesia, Teten Masduki, worried that Indrawati's successor would not take on the vested interests who stand to lose most from a genuine war on corruption.

"Her departure will badly affect bureaucratic reform in Indonesia. The next finance minister could be easily pushed around," he said. "The finance ministry is a huge source of money. It will be a target for corruption, especially for political funding."